The human immunodeficiency virus-1 (HIV-1) is responsible for a global epidemic, with over 33 million infected people worldwide. The lifecycle of HIV-1 has been extensively studied in the hope of identifying a therapeutic intervention that blocks viral transmission or viability. As an example, the Highly Active Anti-Retroviral Therapy (HAART) is a therapeutic approach targeting one or more stages of the HIV-1 life cycle. Favorable clinical results with HAART have shown that simultaneously targeting distinct stages of the viral life cycle may reduce the viral evolutionary escape mechanism that leads to drug resistance. Further, HAART may be more effective if administered simultaneously with other drugs that interrupt the initial entry stage of the virus life cycle. Unfortunately, existing entry inhibitors suffer from weak potency and toxicity issues.
The entry of HIV-1 into the host cell is mediated by interaction of a trimeric gp120/gp41 envelope (Env) protein complex with both cellular CD4 and chemokine co-receptor CCR5 or CXCR4. Each virus Env spike consists of a trimer of two non-covalently associated glycoproteins, an inner gp41 transmembrane protein and an outer gp120 protein. The first step of viral entry is the interaction with CD4, leading to structural changes in the virus Env spike and exposing the chemokine binding domains of gp120. A structural change in the envelope spike exposes the fusion peptide sequence of gp41 and enables the collapse of gp41 into a six-helix bundle, leading to downstream membrane fusion and productive infection.
The HNG class of triazole conjugated peptides was derived from the 12-mer parental peptide 12p1 by converting the proline at residue 6 of 12p1 into an azido-proline and performing copper-catalyzed (2+3) cycloaddition reactions of the azide with substituted acetylenes. As a class, the HNG compounds have enhanced binding affinity for HIV-1 gp120, and block both CD4 and co-receptor sites with great efficacy. The HNG compounds appear to trap the gp120 protein in a non-functional state, distinct from the flexible ground state of gp120 or the CD4 induced conformation, and thus effectively halt the entry process at the initial binding stages. Using pseudotyped HIV-1 as well as isolated recombinant protein mutants, a binding footprint for the ferrocenyl triazole peptides was found to involve D474 and T257. These residues are adjacent to but not directly overlapping the CD4 binding site, and also overlap residues important for BMS-806 inhibition and a recently identified neutralizing antibody epitope. All of the 12p1 family members tested to date inhibit the binding of gp120 to both sCD4 (in a seemingly non-competitive manner) and the co-receptor surrogate mAb17b.
As an example, the ferrocenyl triazole conjugate HNG156 [SEQ ID No:1, wherein X is (2,4)-4-(4-ferrocenyl-1H-1,2,3-triazol-1-yl)pyrrolidine-2-carboxylic acid; also known as (S)-4-((S)-2-((S)-2-((2S,4S)-1-(L-arginyl-L-isoleucyl-L-asparaginyl-L-asparaginyl-L-alloisoleucyl)-4-(4-ferrocenyl-1H-1,2,3-triazol-1-yl)pyrrolidine-2-carboxamido)-3-(1H-indol-3-yl)propanamido)-3-hydroxypropanamido)-5-(((S)-1-(((S)-1-(((S)-1-amino-4-(methylthio)-1-oxobutan-2-yl)amino)-4-(methylthio)-1-oxobutan-2-yl)amino)-1-oxopropan-2-yl)amino)-5-oxopentanoic acid] binds to monomeric gp120 with a KD of 7 nM, in contrast to the 2,600 nM KD value of 12p1. HNG156 inhibition of the co-receptor binding site appears to be allosteric and involves conformational entrapment of Env gp120 into an inactivated state. HNG156 neutralizes viral infection by subtype A, B and C isolates (IC50 range=0.08-62.5 μM), but not viruses pseudotyped with VSV-G. HNG156 also exhibits no detectable toxicity in a tissue explants model at concentrations up to 100 μM. Enhancement of lifetime and potency of the HNG compounds could improve their potential as therapeutic and microbicide agents.
There is a need in the art to develop novel compounds that are useful for treating or preventing HIV-1 infection. There is also a need in the art to develop novel virolytic agents, which could cause virus lysis and prevent viral infection even in the absence of cells. The present invention fulfills these needs.